Implanting in objects (anime) or living creatures (Crystal) to turn into a daimon.
In the anime, the Daimon eggs were created by Professor Tomoe which were used to find a person with a pure heart. The egg would be implanted into an object, fuse with the object, and turn into a Daimon. After a Daimon is destroyed, the egg would separate from the object that it was implanted in and break, releasing a malicious looking puff of black smoke leaving behind a broken shell.
In the crystal, these eggs were black. Pharaoh 90 brought them to Earth when he first contacted Professor Tomoe. Professor Tomoe manufactured and experimented on them in his lab, and the other members of the Death Busters could summon the eggs to create Daimons to assist them when fighting the Senshi. When they were put into a living creature (either intentionally or accidently), a monsterous Daimon would hatch from the egg and emerge from within the host, completely engulfing the host. Once the Daimon is destroyed, the host is left unharmed from the attack and the Daimon egg is ejected from the host and dissolves leaving no trace of it behind. With the exception of Pharaoh 90, and Mistress 9 (who came from a Daimon egg planted in Hotaru), all the members of the Death Busters had a Daimon egg implanted within them.